Am. J. Respir. Crit. Care Med., Vol 150, No. 6, Dec 1994, 1564-1568.
Comparative evaluation of diaphragmatic activity during pressure support ventilation and intermittent mandatory ventilation in animal model
A Uchiyama, H Imanaka, N Taenaka, S Nakano, Y Fujino and I Yoshiya
Intensive Care Unit, Osaka University Hospital, Suita, Japan.
The aim of the present study is a comparative evaluation of the effects of
pressure support ventilation (PSV) and intermittent mandatory ventilation
(IMV) on diaphragmatic activity in rabbit model of neonate. The animals
were divided into a PSV group and an IMV group. In the IMV group,
spontaneous breathing and four kinds of IMV rate (5, 10, 15, and 20/min)
were applied (Ventilator: Bear BP200, peak inspiratory pressure [PIP]: 12
cm H2O, inspiratory time: 0.6 s). In the PSV group, spontaneous breathing
and four levels of PSV (3, 6, 9, and 12 cm H2O) were applied (Ventilator:
VIP Bird, flow triggering). Airway pressure (Paw), flow (V), esophageal
pressure (Pes), integrated diaphragmatic electromyogram (Edi), and arterial
gas data were measured. Amplitudes of Pes and Edi were expressed as
percentages (% Edi and % Pes) of the control value during spontaneous
breathing to evaluate diaphragmatic activity. Lower IMV rates did not
reduce diaphragmatic activity. Approximately half of diaphragmatic activity
of control remained even at IMV 15/min. Diaphragmatic activity disappeared
at IMV20/min. In contrast, PSV reduced Edi and Pes linearly according to
support level. In conclusion, diaphragmatic activity could be reduced more
gradually with PSV than IMV by altering ventilatory support level.
